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At least 973 records · Page 54Linked to original sources
PubMed2005

Herkogamy and mating patterns in the self-compatible daffodil Narcissus longispathus.

BACKGROUND AND AIMS: Floral design in self-compatible plants can influence mating patterns. This study investigated Narcissus longispathus, a self-compatible bee-pollinated species with wide variation in anther-stigma separation (herkogamy), to determine the relationship between variation in this floral trait and the relative amounts of cross- and self-fertilization. METHODS: Anther-stigma separation was measured in the field in six populations of N. longispathus from south-eastern Spain. Variation in herkogamy during the life of individual flowers was also quantified. Multilocus outcrossing rates were estimated from plants differing in herkogamy using allozyme markers. KEY RESULTS: Anther-stigma separation varied considerably among flowers within the six populations studied (range = 1-10 mm). This variation was nearly one order of magnitude larger than the slight, statistically non-significant developmental variation during the lifespan of individual flowers. Estimates of multilocus outcrossing rate for different herkogamy classes (t(m) range = 0.49-0.76) failed to reveal a monotonic increase with increasing herkogamy. CONCLUSIONS: It is suggested that the lack of a positive relationship between herkogamy and outcrossing rate, a result that has not been previously documented for other species, could be mostly related to details of the foraging behaviour of pollinators.

Flowers↗
PubMed2005

Mode of pollen-tube growth in Pistils of Myrica rubra (Myricaceae): a comparison with related families.

BACKGROUND AND AIMS: It is generally known that fertilization is delayed for more than a few weeks after pollination in Fagales. Recent studies showed that, during that period, pollen tubes grew in pistils in close association with the development of the ovule in a five-step process in Casuarina (Casuarinaceae) and a four-step process in Alnus (Betulaceae). The number of pollen tubes was reduced from many to one, a fact suggesting that delayed fertilization plays a role for gametophyte selection. Myrica (Myricaceae) also shows delayed fertilization for >2 weeks after pollination, but nothing is known of how pollen tubes grow in the pistil during that period. METHODS: Pollen-tube growth and the development of the ovule in pistils was investigated by fluorescent and scanning electron microscopy and analysis of microtome sections of the pistils. KEY RESULTS: Developmental study of the pollen-tube growth in the pistil of M. rubra showed that the tip of the pollen tube was branched or lay in a zigzag pattern in the upper space of the ovarian locule or near the tip of the integument, and subsequently was swollen on the nucellar surface. Such morphological changes indicate that the pollen-tube growth was temporarily arrested before fertilization. The pollen-tube growth in M. rubra can therefore be summarized as occurring in three steps: (1) from the stigma to the ovarian locule; (2) from the ovarian locule to the nucellar surface; and (3) from the nucellar surface to the embryo sac. CONCLUSION: Myrica differs from other families in that the pollen tubes arrest their growth on the nucellar surface, probably digesting nutrient from nucellar cells. There is little information on five other families of Fagales. An extensive study is needed to better understand the diversity and function of the mode of pollen-tube growth within the order.

Betulaceae↗
PubMed2005

Nectar concentration and composition of 26 species from the temperate forest of South America.

BACKGROUND AND AIMS: Floral nectar concentration and chemical composition of 26 plant species native to the temperate forest of southern South America are reported and the relationships with the flower type are evaluated. METHODS: Nectar concentration was measured with a hand refractometer and sugar composition was analysed by gas-liquid chromatography. Plant species were classified into flower type categories based not only on floral features but also on data from the literature and field observations on their pollinators. KEY RESULTS: Most data on nectar are new reports at the generic and/or specific level. Plant species in which more than one population was studied showed significant among-population variation in nectar sugar concentration and composition. Results showed a weak relationship between nectar traits and flower type. Many species had nectar containing 50 % or more sucrose (17 of 26 species), independent of the main pollinator. CONCLUSIONS: Considering that (a) nectar characteristics did not show a clear association with different flower types or with plant taxonomic membership, and (b) different populations of the same species showed large variability in sugar composition, the results suggest that other factors (e.g. historical and environmental) could be involved in determining the sugar composition of the highly endemic plant species from this region.

Carbohydrates↗
PubMed2006

The impact of cell division and cell enlargement on the evolution of fruit size in Pyrus pyrifolia.

BACKGROUND AND AIMS: Dramatic increases in fruit size have accompanied the domestication of Pyrus pyrifolia. To evaluate the contribution of cell division and cell enlargement in the evolution of fruit size, the following study was conducted. METHODS: Three wild Pyrus and 46 cultivated Pyrus pyrifolia cultivars were selected to examine cell number/size at time of pollination and at time of fruit harvest. The period of cell division was estimated by logarithmic curve of the increasing pattern of cell number, and its correlations with maturation period and final fruit size were analysed. KEY RESULTS: Final fruit size is directly related to the number of cells produced in the period immediately following pollination. Late-maturing cultivars are larger than earlier-maturing cultivars and this is due to an extended period of cell division. CONCLUSIONS: The evolution of fruit size in P. pyrifolia has mainly resulted from shifts in the ability of cells to divide rather than to enlarge.

Biological Evolution↗
PubMed2005

Mapping genome-genome epistasis: a high-dimensional model.

MOTIVATION: The proper development of any organ or tissue requires the coordinated expression of its underlying genes that can be located on different genomes present in an organism. For instance, each step in the development of seed for a higher plant is the consequence of gene interactions from the maternal, embryo and endosperm genomes. RESULTS: We present a multivariate statistical model for mapping quantitative trait loci (QTL) by incorporating two important aspects of seed development in plants-QTL interactions derived from different genomes, the maternal, embryo and endosperm, and genetic correlations among phenotypic traits expressed in different genome-specific tissues. This model, which has a high dimensionality, is constructed within the maximum-likelihood context based on a finite mixture model. The implementation of the expectation-maximization algorithm allows for the efficient estimation of QTL positions, their action and interaction effects and pleiotropic effects. The application of this high-dimensional model to a real rice dataset has validated its usefulness. CONCLUSIONS: Our model was derived for self-pollinated plants, but it can be extended to cross-pollinated plants and to animals. With the burgeoning of genetic and genomic data, this high-dimensional model will have many implications for agricultural and evolutionary genetic research. AVAILABILITY: A package of software will be provided from the corresponding author upon request.

Chromosome Mapping↗
PubMed2026

Phylotranscriptomics Allows Distinguishing Major Gene Flow Events from Incomplete Lineage Sorting in Rapidly Diversifying Mimetic Orchids (Genus Ophrys).

Ophrys orchids (or bee orchids) provide an outstanding example of a plant adaptive radiation. Over the last 5 million years, this genus has diversified into hundreds of taxa as a result of its unconventional pollination strategy, known as "sexual swindling". However, the rapid and substantial diversification of this genus, combined with its capacity for hybridization and large genome size, poses significant challenges in addressing its systematics. We used phylotranscriptomics as a genome complexity reduction technique to infer the phylogenetic relationships among Ophrys main lineages. More than seven thousand gene trees enabled us to determine the relative contributions of gene flow and incomplete lineage sorting (ILS) in Ophrys evolution. First, we propose a new phylogenetic hypothesis for the genus with an unprecedented resolution that largely confirms the relationships between the main Ophrys lineages, but also provides new insights within each subgenera. By combining phylogenetic network inference with introgression analyzes based on gene tree topologies and branch lengths, we then show that the numerous phylogenetic incongruences among gene tree topologies result from a pervasive background of ILS, over which stand out several well-supported, ancient and potentially adaptive gene flow events between lineages. These major gene flow events provide a new perspective on the evolution of the Ophrys genus and its pollination, questioning previous hypotheses inferred without considering its reticulate evolution, and providing a better understanding of discrepancies observed among previous phylogenetic studies of the genus.

Orchidaceae↗
PubMed1986

The Mu transposable elements of maize: evidence for transposition and copy number regulation during development.

The Mu transposon of maize exists in a highly mutagenic strain called Robertson's Mutator. Plants of this strain contain 10-50 copies of the Mu element, whereas most maize strains and other plants have none. When Mutator plants are crossed to plants of the inbred line 1S2P, which does not have copies of Mu, the progeny plants have approximately the same number of Mu sequences as did their Mutator parent. Approximately one-half of these copies have segregated from their parent and one-half have arisen by transposition and are integrated into new positions in the genome. This maintenance of copy number can be accounted for by an extremely high rate of transposition of the Mu elements (10-15 transpositions per gamete per generation). When Mutator plants are self-pollinated, the progeny double their Mu copy number in the first generation, but maintain a constant number of Mu sequences with subsequent self-pollinations. Transposition of Mu and the events that lead to copy number maintenance occur very late in the development of the germ cells but before fertilization. A larger version of the Mu element transposes but is not necessary for transposition of the Mu sequences. The progeny of crosses with a Mutator plant occasionally lack Mutator activity; these strains retain copies of the Mu element, but these elements no longer transpose.

Base Sequence↗
PubMed2003

A consensus linkage map for sugi (Cryptomeria japonica) from two pedigrees, based on microsatellites and expressed sequence tags.

A consensus map for sugi (Cryptomeria japonica) was constructed by integrating linkage data from two unrelated third-generation pedigrees, one derived from a full-sib cross and the other by self-pollination of F1 individuals. The progeny segregation data of the first pedigree were derived from cleaved amplified polymorphic sequences, microsatellites, restriction fragment length polymorphisms, and single nucleotide polymorphisms. The data of the second pedigree were derived from cleaved amplified polymorphic sequences, isozyme markers, morphological traits, random amplified polymorphic DNA markers, and restriction fragment length polymorphisms. Linkage analyses were done for the first pedigree with JoinMap 3.0, using its parameter set for progeny derived by cross-pollination, and for the second pedigree with the parameter set for progeny derived from selfing of F1 individuals. The 11 chromosomes of C. japonica are represented in the consensus map. A total of 438 markers were assigned to 11 large linkage groups, 1 small linkage group, and 1 nonintegrated linkage group from the second pedigree; their total length was 1372.2 cM. On average, the consensus map showed 1 marker every 3.0 cM. PCR-based codominant DNA markers such as cleaved amplified polymorphic sequences and microsatellite markers were distributed in all linkage groups and occupied about half of mapped loci. These markers are very useful for integration of different linkage maps, QTL mapping, and comparative mapping for evolutional study, especially for species with a large genome size such as conifers.

Base Sequence↗
PubMed2003

Honey bee (Hymenoptera: Apidae) foraging in response to preconditioning with onion flower scent compounds.

Onion (Allium cepa L.) seed production has long been plagued with yield problems because of lack of pollination by the honey bee, Apis mellifera L. To attempt to attract more pollinators to the onion seed production field, honey bees were conditioned to associate onion floral odor components with a reward. Isolated nucleus hives of honey bees were fed 30% sucrose solutions scented with a 0.2% solution of onion floral odor compounds. After feeding on these solutions for 6 wk, bees were not found to prefer onion flowers to two competing food sources, carrot and alfalfa flowers, at the 5% significance level. However, there was an overall trend indicating a change in honey bee behavior, with fewer "trained" bees visiting alfalfa and carrot and more visiting onion. Thus, it may be possible to alter honey bee behavior with preconditioning but probably not to a degree that would be economically significant.

Animals↗
PubMed2004

Brood pheromone regulates foraging activity of honey bees (Hymenoptera: Apidae).

Brood pheromone modulated the foraging behavior of commercial honey bee, Apis mellifera L., colonies pollinating a 10-ha market garden of cucumber, Cucurbita pepo L., and zucchini, Cucumis saticus L., in Texas in late autumn. Six colonies were randomly selected to receive 2000 larval equivalents of brood pheromone and six received a blank control. The ratio of pollen to nonpollen foragers entering colonies was significantly greater in pheromone-treated colonies 1 h after treatment. Pheromone-treated foragers returned with pollen load weights that were significantly heavier than controls. Pollen returned by pheromone-treated foragers was 43% more likely to originate from the target crop. Number of pollen grains washed from the bodies of nonpollen foragers from pheromone-treated colonies was significantly greater than controls and the pollen was 54% more likely to originate from the target crop. Increasing the foraging stimulus environment with brood pheromone increased colony-level foraging and individual forager efforts. Brood pheromone is a promising technology for increasing the pollination activity and efficiency of commercial honey bee colonies.

Animals↗
PubMed2001

Water deficit inhibits cell division and expression of transcripts involved in cell proliferation and endoreduplication in maize endosperm.

Water deficit at the early post-pollination stage in cereal grains decreases endosperm cell division and, in turn, decreases the capacity for storage material accumulation. Post-mitotic replication of nuclear DNA (endoreduplication) may also play a role in stress effects. To gain a better understanding of the extent to which cell proliferation and endoreduplication are affected by water deficit, nuclear numbers and size were examined in endosperms of maize (Zea mays L.) by flow cytometry and the transcript levels of genes which have recognized roles in the cell cycle were quantified. Water deficit from 5-13 d after pollination (DAP) decreased the rate of endosperm cell division by 90% and inhibited [3H]-thymidine incorporation into DNA from 9-13 DAP. The proportion of nuclei engaging in endoreduplication and nuclear DNA content increased steadily from 9-13 DAP in controls, but water deficit initially increased the proportion of endoreduplicating nuclei at 9 DAP, then halted further entry into endoreduplication and S-phase cycling from 9-13 DAP. Transcript levels of alpha-tubulin, and the S-phase gene products histone H3 and PCNA were not affected by water deficit until 13 DAP, whereas those of ZmCdc2, a cyclin dependent kinase (CDK) with regulatory roles in mitosis, were inhibited substantially from 9-13 DAP. Cell proliferation and associated processes were inhibited at initial stages of the stress episode, whereas endoreduplication and associated S-phase processes were not inhibited until the stress was more advanced. It was concluded that endosperm mitosis has greater sensitivity than endoreduplication to water deficit.

Adaptation, Physiological↗
PubMedDate not supplied

Genetic structure, mating system, and long-distance gene flow in heart of palm (Euterpe edulis Mart.).

We report a detailed analysis of the population genetic structure, mating system, and gene flow of heart of palm (Euterpe edulis Mart.-Arecaceae) in central Brazil. This palm is considered a keystone species because it supplies fruits for birds and rodents all year and is intensively harvested for culinary purposes. Two populations of this palm tree were examined, using 18 microsatellite loci. The species displays a predominantly outcrossed mating system (tm = 0.94), with a probability of full sibship greater than 70% within open-pollinated families. The following estimates of interpopulation genetic variation were calculated and found significant: FIT = 0.17, FIS = 0.12, FST = 0.06, and RST = 0.07. This low but significant level of interpopulation genetic variation indicates high levels of gene flow. Two adult trees were identified as likely seed parents (P > 99.9%) of juveniles located at a distance of 22 km. Gene flow over such distances has not been reported before for tropical tree species. The establishment and management of in situ genetic reserves or ex situ conservation and breeding populations for E. edulis should contemplate the collection of several hundreds open-pollinated maternal families from relatively few distant populations to maximize the genetic sampling of a larger number of pollen parents.

Arecaceae↗
PubMed2006

Induction of tetraploid derivatives of maize inbred lines by nitrous oxide gas treatment.

Maize (Zea mays L.) is a model organism for various genetic and physiological studies. Induction of autotetraploid lines from elite inbred lines is valuable for investigating gene dosage effects on the molecular level. We applied nitrous oxide gas at the time of fertilization (30-36 h after pollination) for 20 h on maize inbred line Oh43. The nitrous oxide gas treatment between pressures of 600-1000 kPa proved to be effective in inducing tetraploids. The treatment also significantly increased the rates of germless and shriveled kernels. Twelve inbred lines were treated with nitrous oxide gas for 20 h at either 800 or 900 kPa pressures, 30 or 36 h after pollination. Although tetraploid or tetraploid class aneuploid plants from 9 of 12 inbreds tested were successfully generated, only six genotypes produced progenies. The successful tetraploid inbred lines were from the A188, B73, H99, Oh43, Stock 6, and W22 genetic backgrounds. Aneuploids, plants with broken chromosomes and chimeras, were also found among the treated materials.

Chromosomes, Plant↗
PubMed2003

Self-incompatibility (S) locus region of the mutated S6-haplotype of sour cherry (Prunus cerasus) contains a functional pollen S allele and a non-functional pistil S allele.

This study characterizes the S6m-haplotype, a mutated S6-haplotype with an altered HindIII cut site, of sour cherry (Prunus cerasus). Inheritance and pollination studies of S-haplotypes from reciprocal crosses between 'Erdi Botermo' (EB; S4S6mSa) and 'Rheinische Schattenmorelle' (RS; S6SaSbSc) revealed that the S6m-haplotype conferred unilateral incompatibility with a non-functional pistil component and a functional pollen component. Expression analyses of S6-RNase and SFB6, a candidate gene for pollen-S, in the S6m-haplotype showed that SFB6 was transcribed in EB pollen, but S6-RNase was not transcribed in EB styles. These results were consistent with data from the inheritance and pollination studies. Inverse PCR for the flanking regions of S6-RNase in the S6- and S6m-haplotypes revealed an approximately 2600 bp insertion present at approximately 800 bp upstream of the S6-RNase in the S6m-haplotype, which is responsible for the alternation of the HindIII cut site and a possible cause of inhibition of the transcription of S6-RNase. SFB6 was present downstream of S6-RNase in both the S6- and S6m-haplotypes and expressed in the same way, supporting the idea that SFB is a good candidate for pollen-S in Prunus.

Alleles↗
PubMed2002

OSTF1: a HD-GL2 family homeobox gene is developmentally regulated during early embryogenesis in rice.

In many eukaryotic organisms, homeobox genes are important regulators that specify the cell fate and body plan in early embryogenesis. In this study, a gene designated OSTF1 (Oryza sativa transcription factor 1) encoding a homeodomain protein in rice was isolated and characterized. The encoded OSTF1, although sharing only approximately 51% sequence identity with other HD-GL2 members, contains four characteristic motifs (an N-terminal acidic region, a homeodomain, a truncated leucine zipper, and a START domain). OSTF1 was detected as a single copy gene in rice. The transcripts were absent in young panicle or mature spikelet before anthesis, but appeared very early in the pollinated grain with a transient profile. In vegetative tissues examined, expression was only detectable in root. In situ hybridization analysis on developing grains revealed that OSTF1 was strongly and uniformly expressed in the embryo at the globular stage and preferentially localized to the protoderm at 3-6 d after pollination. Expression was also detectable in the integument and throughout the endosperm. Although OSTF1 is not closely related to the remaining HD-GL2 members in sequences, this gene exhibits an analogous epidermis-preferential expression pattern.

Amino Acid Sequence↗
PubMed2003

CvADH1, a member of short-chain alcohol dehydrogenase family, is inducible by gibberellin and sucrose in developing watermelon seeds.

To understand the molecular mechanisms that control seed formation, we selected a seed-preferential gene (CvADH1) from the ESTs of developing watermelon seeds. RNA blot analysis and in situ localization showed that CvADH1 was preferentially expressed in the nucellar tissue. The CvADH1 protein shared about 50% homology with short-chain alcohol dehydrogenase including ABA2 in Arabidopsis thaliana, stem secoisolariciresinol dehydrogenase in Forsythia intermedia, and 3beta-hydroxysterol dehydrogenase in Digitalis lanata. We investigated gene-expression levels in seeds from both normally pollinated fruits and those made parthenocarpic via N-(2-chloro-4-pyridyl)-N'-phenylurea treatment, the latter of which lack zygotic tissues. Whereas the transcripts of CvADH1 rapidly started to accumulate from about the pre-heart stage in normal seeds, they were not detectable in the parthenocarpic seeds. Treating the parthenogenic fruit with GA(3) strongly induced gene expression, up to the level accumulated in pollinated seeds. These results suggest that the CvADH1 gene is induced in maternal tissues by signals made in the zygotic tissues, and that gibberellin might be one of those signals. We also observed that CvADH1 expression was induced by sucrose in the parthenocarpic seeds. Therefore, we propose that the CvADH1 gene is inducible by gibberellin, and that sucrose plays an important role in the maternal tissues of watermelon during early seed development.

Alcohol Dehydrogenase↗
PubMed1993

Floral biology and breeding behavior in the bamboo Dendrocalamus strictus Nees.

Floral biology and breeding behavior were studied in the bamboo Dendrocalamus strictus Nees. The inflorescence in this species is a large branching panicle. Fertile florets are intermixed with smaller sterile ones. There are six stamens. The ovary is stipitate and turbinate. The style is long and the stigma is bifid and plumose. Dendrocalamus strictus is typically dichogamous and protogynous. The gynoecium matures 3-4 days before the androecium, effectively preventing self pollination. Flower bloom, which took place over a period of 2 to 3 h, was dependent on air temperature and only occurred between 0600 and 1300 h. Dendrocalamus strictus is anemophilous. Flowers in the male phase were visited by insects. These insects completely neglected the flowers at the female phase. The insects fed on the pollen and were not pollen vectors. When wind was excluded by enclosing the inflorescences in bags there was no seed set, indicating that cross pollination by wind is necessary for fertilization and that parthenocarpy and apomixis are not occurring in this species. Pollen fertility was about 98% as indicated by staining fresh pollen at the time of anther dehiscence and pollen release with Alexander's stain (Alexander 1969). When placed on a modified Brewbaker-Kwak medium containing 1% glucose, the pollen grains germinated well, and the pollen tubes grew to 15-20 times the diameter of mature pollen grains. Although profound protogyny has its disadvantages in times of sporadic flowering, it can be useful in breeding programs because it eliminates the need for emasculation.

Journal Article↗
PubMedDate not supplied

Pollen management for intensive seed orchard production.

Artificially increasing pollen supply (supplemental mass pollination (SMP)) to conifer seed orchards has the potential to increase seed yields and improve the genetic worth of seed crops that would otherwise suffer from the detrimental effects of pollen contamination and unbalanced paternal contribution. However, success rates, measured as the proportion of seed fertilized by SMP, have been low. This review examines the concepts underlying SMP and presents data for two SMP field trials with Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and white/Engelmann spruce (Picea glauca (Moench) Voss, Picea engelmannii Parry ex Engelm.). The trial results are discussed with respect to pollen fertility, pollination technique, and competing pollen cloud density. I also summarize methods for ensuring the successful handling of pollen ex situ.

Journal Article↗